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Biomedical subjects

K Mueller

Publications and source records attributed to K Mueller.

At least 109 records · Page 6Linked to original sources
PubMed1977

Specificity of cholecystokinin satiety effect: reduction of food but not water intake.

The C-terminal octapeptide of cholecystokinin (CCK) was injected into water-deprived rats to observe the effect on water and milk intake. The doses used were 0, 20, and 40 Ivy dog units/kg. The data indicated that milk intake was suppressed in a dose-related fashion within 2-4 min of injection but water intake was not suppressed. This satiety hormone is thus specific to food intake.

Analysis of Variance↗
PubMed1977

Capacity of ribosomal RNA promoters of E. coli to bind RNA polymerase.

The rate of in vitro transcription of the rRNA genes of E. coli is more than 20 fold higher than the averaged transcription rate of other genome segments of the same size. This "preferential transcription" of rRNA genes reflects a high efficiency of their promoters in chain initiation. We show that the high initiation rate at rRNA promoters results from a high rate of RNA polymerase binding to these promoters as measured by the formation of heparin-resistant RNA polymerase-DNA complexes. The results indicate that the preferential binding of RNA polymerase to rRNA promoters is mainly due to their large binding capacity rather than to a high rate constant of polymerase binding to a single binding site. The polymerase binding capcity of rRNA promoters was estimated from the number of rRNA chains initiated by heparin-resistant complexes under conditions of template saturation and from the number of rRNA transcription units participating in the binding reaction. At least 30 RNA polymerase molecules were found to be protected from heparin per rRNA transcription unit. The rest of the genome (99.4%; possibly sufficient to encode 4000 nonribosomal RNA species) protects under these conditions 2000 enzyme molecules. These results suggest that a high multiplicity of RNA polymerase binding may be responsible for the high efficiency of rRNA promoters. The validity of this hypothesis is discussed.

DNA, Bacterial↗
PubMedDate not supplied

Glycolytic ATP production estimated from 31P magnetic resonance spectroscopy measurements during ischemic exercise in vivo.

In an oxygen-depleted muscle, glycolytically produced ATP is inversely related to the ([ATP]+ creatine phosphate [PCr]) decrease because ATP, PCr, and glycolysis are virtually the only energy sources under these conditions. In particular, the onset of glycolysis or any appreciable increase in the rate of glycolytic ATP production will lead to a slower rate of ([ATP]+ [PCr]) breakdown at a given energy consumption. To quantify this relationship, endurance athletes performed isometric foot plantar flexion (20% of a test force [TF], n = 10; 50% TF, n = 5) during local arterial occlusion. Parameters of energy metabolism were measured with 31P magnetic resonance spectroscopy (31P-MRS). During exercise, [PCr] decreased to 80 +/- 10 (20% TF) and 11 +/- 4% (50% TF) of its resting concentration, and pH dropped from 7.04 +/- 0.01 to 6.98 +/- 0.10 (20% TF) and from 7.03 +/- 0.02 to 6.70 +/- 0.10 (50% TF). In both experiments, two phases of ([ATP]+ [PCr]) decrease were observed: an initial faster decrease was followed by a slower decline. The latter phase started at about the time when the pH began to drop. The difference between a line extrapolated from the slope of the initial phase and the measured ([ATP]+[PCr]) decrease was used as an estimate for glycolytically produced ATP. This estimate and pH were significantly correlated with r = -0.97 (20% TF) and r = -0.99 (50% TF). These results indicate that glycolytically produced ATP can be estimated from the ([ATP]+ [PCr]) decrease during exercise.

Adenosine Triphosphate↗